Magnetizers for pigging tools

ABSTRACT

Circumferential and axial magnetizers for a magnetic flux leakage pig. A circumferential magnetizer module for a smart pig comprises a central shaft and at least one magnet bar for inducing a magnetic field transverse to a longitudinal axis of the shaft. The magnet bar comprises at least one magnet, and a means for collapsing radially inward to the shaft. A sensor head disposed between circuit poles at each polar end of the magnet monitors magnetic flux. An axial magnetizer module comprises a central shaft and at least one magnet bar to induce a magnetic field coaxially to a longitudinal axis of the shaft. Magnets of opposite polarity are circumferentially disposed around ends of the central shaft. A sensor head disposed between circuit poles at each polar end monitors magnetic flux. The central shaft of a circumferential magnetizer or axial magnetizer may comprise a joint linking an additional smart pig module.

CROSS-REFERENCE

This application claims benefit under 35 U.S.C. § 119(e) of ProvisionalU.S. Patent Application No. 62/373,902, filed Aug. 11, 2016 andProvisional U.S. Patent Application No. 62/448,811, filed Jan. 20, 2017,the contents of which is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The present disclosure relates to apparatus and systems for inspectingpipelines. More specifically, the present disclosure relates toapparatus and systems for detecting structural defects, flaws, and otherdamage in pipeline systems.

BACKGROUND

The energy infrastructure of the world depends on pipelines. Pipelinestransport crude oil and unrefined gas from wells to refineries andtransport refined products to chemical plants, utilities, localdistribution units, homes, airports, and nearly every place that usesenergy. Energy pipelines include liquid petroleum pipelines and naturalgas pipelines.

Pipelines can vary in size depending on purpose. For example, inoil-producing locations, gathering pipelines may be as small as twoinches in diameter. The Trans-Alaska Pipeline, in contrast, whichtransports crude oil, is about 48 inches in diameter. Pipelines ofvarying sizes and purposes have diameters in between.

Given the materials being transported, pipelines present health, safety,environmental, and security concerns. Pipeline and energy companies areeconomically incentivized to bring as much product as possible fromsource to destination. The various governments also regulate pipelinesand pipeline-transported materials extensively. To prevent release ofpipeline-transported materials, pipeline and energy companies conductintegrity management programs continuously.

Integrity management programs include inspections to determine theintegrity of pipeline systems. To this end, inspections may identifyearly indications of future problems, such as corrosion, cracks,mechanical damage, and dent and bend strain locations that may havedefects that can cause failures in the future. Pipeline inspectioncompanies have developed specialized tools to inspect the full body ofpipelines, including inline inspection tools commonly referred to assmart pigs.

Smart pigs travel through the interior of a pipeline, often withoutstopping the flow of medium through the pipeline. These pigs may collectgigabytes of data about a pipeline including wall thickness, geometricalshape, corrosion, pitting, cracks, holes, dents, and other potentialsources of problems. Identifiable flaws include, but are not limited to,metal loss caused by corrosion, erosion, pipe manufacturing, andconstruction of pipelines. These flaws may also include some forms ofaxially oriented flaws, such as narrow axial metal loss, hook cracks,lack of fusion, and fatigue-related cracking. These flaws may alsoinclude circumferentially oriented flaws of a similar nature. Mechanicaldamage may also be identified, including dents, gouges, cracks, andcombined defects (e.g., a gouge near a pipe seam), and these types ofdamage may also be oriented either axially or circumferentially. Pigsuse various, specialized sensing systems to automatically andcontinuously collect and store this data. Related software is typicallyused to interpret the data and aid operators in identifying significantflaws in order to investigate and make the necessary repairs to helpprevent failures.

Pigs used for in-line inspection of pipelines may employ one or more ofseveral technologies, including but are not limited to ultrasonictechnology (“UT”) for wall thickness measurements or crack detection,electromagnetic acoustic transducer (“EMAT”) technology, magnetic fluxleakage (“MFL”) technology, pipe surface profiling commonly referred toas geometry or caliper technology, and inertial mapping of pipelocations and detection of ground movement (“IMU”). MFL is anondestructive method of testing that employs a magnetic flux leakageprinciple to detect certain defects and potential problems found in thefull body of a pipeline. MFL can be used only in pipelines made offerromagnetic metals, such as carbon based steels. Powerful magnets,including permanent or electromagnets, magnetize portions of thepipeline, and sensors may be generally placed between the poles of themagnets to monitor the changes in flux leakage from the pipeline inareas experiencing various flaws where the cross sectional area isreduced by metal loss or where a fissure or crack perpendicular to thedirection of the magnetic field causes a detectable change in themagnetic leakage field. Automated feature searches and human analysiscan provide comprehensive reporting, prioritizing, and quantifying theseverity of flaws. This information is then used by the pipelineoperators to facilitate field investigations, repairs, and futureinspection intervals.

SUMMARY

The present disclosure relates to pigs utilizing magnetic flux leakagetechnology. An embodiment of the present disclosure relates to MFL pigshaving one or more circumferential magnetizers. Another embodiment ofthe present disclosure relates to MFL pigs having one or more axialmagnetizers. Yet another embodiment of the present disclosure relates toMFL pigs having at least one of a circumferential magnetizer and atleast one of an axial magnetizer.

A pig may be cylindrical in shape and sized to fit the diameter of thepipeline being inspected. A pig may include one or more componentbodies. Where a pig includes two or more component bodies, the componentbodies may be operatively connected. For example, an MFL pig may includethree or more component bodies operatively connected to each other, twoor more of the component bodies including magnetizers comprising magnetsand sensors, and another component body including batteries, datastorage, and various electronics. In some embodiments, a pig may includemore than three component bodies. For example, a pig may include threecircumferential magnetizers, an axial magnetizer, an electronics body, ageometry body, an IMU body, and a battery body. In an embodiment, theaxial or circumferential magnetizers may be offset from each other toprovide complete circumferential sensor coverage of the pipe.

A magnetizer on an MFL pig may use permanent magnets or electromagnets.In an embodiment, a magnetizer may use rare-earth magnets, for exampleneodymium-based magnets. Rare-earth magnets, such as neodymium-basedmagnets, may be plated with a metal layer. For example, neodymium-basedmagnets may be plated with a thin nickel layer.

In an embodiment, each magnetizer module may be arranged with four ormore magnet bars. In an embodiment, each magnetizer module may bearranged with six magnet bars. Each magnet bar may provide a localizedcircuit to bring the magnetic flux density in the pipe wall to nearsaturation levels. For example, the flux density in the pipe wall may bebrought equal to or greater than 1.6 Tesla. One of skill in the art willrecognize that the number, type, and location of the magnets or magnetbars may be altered in various ways and still achieve saturation, forexample, a magnetic flux density of about 1.6 Tesla.

Each of the magnet bars may be attached to a center shaft extendingabout a central axis of the magnetizer. The magnet bars may extendradially outward from the central shaft, which may have an axiscoextensive with the direction of the pipeline. A circumferentialmagnetizer may create a magnetic field orientation in a directiontransverse to the axis of a pipeline. An axial magnetizer may create amagnetic field orientation in a direction corresponding to the axis of apipeline.

Hall-effect sensors (or other high-sensitivity sensors), may be placedon each magnet bar between the north and south poles. The sensors, orthe sensor heads on which the sensors may be affixed, may be coupled tothe central shaft. These sensors may monitor the changes in the magneticfield, which may leak from the internal pipe surface. Changes in fluxleakage may occur at areas with corrosion or metal loss, geometricdeformations, dents, buckles, wrinkles, and different forms of cracking.Software and human analysis can identify damaged areas and determine theextent of damage. For example, the MFL pig and accompanying software anddata analysis may identify the length, width, depth, and location offlaws in the pipeline.

In an embodiment, the pig may include a plurality of sensors. In a moredetailed embodiment, the plurality of sensors may include at least oneHall sensor. In an alternate embodiment, the plurality of sensors mayinclude at least one ultrasonic or eddy-current sensor. Some embodimentsmay include one or more Hall-effect sensors and one or more ultrasonicor eddy-current sensors. In an embodiment, one or more sensors may bedisposed on a sensor head, which may have a sloping trapezoid, rhomboid,rectangle, or parallelogram shape.

A sensor head may include a suspension system for positioning andbiasing the sensor head. In an embodiment, a sensor head may bepositioned and biased with one or more conical springs to allowcontinuous tracking of the internal surface of the pipe. In anembodiment, a plurality of sensors may be disposed on an articulating,radial floating sensor head to continuously track the surface of thepipeline.

In an embodiment, a pig according to the present disclosure may includeone or more magnet bar wear pads. A magnet bar wear pad, in anembodiment, may be arranged and designed to facilitate slowcounter-clockwise rotation of a magnetizer or pig.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description, taken in conjunctionwith the accompanying drawings. Understanding that these drawings depictonly several embodiments in accordance with the disclosure and aretherefore, not to be considered limiting of its scope. The disclosurewill be described with additional specificity and detail through use ofthe accompanying drawings.

In the drawings:

FIG. 1 depicts an MFL pig having a plurality of operatively connectedcomponent bodies in accordance with an embodiment of the presentdisclosure;

FIG. 2 presents a side view of a portion of an MFL pig having aplurality of operatively connected component bodies in accordance withan embodiment of the present disclosure;

FIG. 3 is a sectional schematic diagram of a circumferential magnetizer;

FIG. 4 depicts a schematic diagram of a magnet bar and shows thedirection of the magnetic field in relation to the sensors and acrack-like defect, in accordance with an embodiment of the presentdisclosure;

FIG. 5 presents an illustration of sensor placement relative to magnetand magnet bar placement on a circumferential magnetizer in accordancewith an embodiment of the present disclosure;

FIG. 6 shows a top view of a circumferential magnet bar in accordancewith an embodiment of the present disclosure;

FIG. 7 depicts a perspective view of a circumferential magnetizer inaccordance with an embodiment of the present disclosure;

FIG. 8 shows a plurality of circumferential magnetizers according to anembodiment of the present disclosure operatively linked together andnavigating bends in a pipeline;

FIG. 9 shows a plurality of circumferential magnetizers and theirmechanical relationship to each other according to an embodiment of thepresent disclosure;

FIG. 10 shows perspective views of two circumferential magnetizers toillustrate the relationship of the magnet bars according to anembodiment of the present disclosure;

FIG. 11 shows the suspension system of the magnet bars and illustratesthe ability of the magnet bars to track the pipe surface according to anembodiment of the present disclosure;

FIG. 12 presents a side perspective view of a circumferential magnetizeraccording to an embodiment of the present disclosure;

FIG. 13 shows a cross sectional view of one of the magnetizer modulesshowing key components of the design, according to an embodiment of thepresent disclosure;

FIG. 14 shows a side view of an embodiment of a circumferentialmagnetizer with a magnet bar removed to illustrate certain features;

FIG. 15 shows a cross-section of a side view of a circumferentialmagnetizer in accordance with an embodiment of the present disclosure;

FIG. 16 shows exemplary axial magnetizer modules coupled together inaccordance with an embodiment of the present disclosure;

FIG. 17 shows front and side views of an exemplary axial magnetizer inaccordance with an embodiment of the present disclosure;

FIG. 18 shows a side view of an embodiment of an axial magnetizer with amagnet bar removed to illustrate certain features; and

FIG. 19 a cross-section of a side view of an axial magnetizer inaccordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described herein arenot meant to be limiting. Other embodiments may be utilized, and otherchanges may be made, without departing from the spirit or scope of thesubject matter presented here. It will be readily understood that theaspects of the present disclosure, as generally described herein, andillustrated in the Figures, may be arranged, substituted, combined, anddesigned in a wide variety of different configurations, all of which areexplicitly contemplated and make part of this disclosure.

This disclosure is generally drawn to apparatus and systems forinspecting pipelines. Examples of this disclosure may be drawn to pigsand pigging systems, smart pigs, MFL pigs, circumferential magnetizersfor MFL pigs, and axial magnetizers for MFL pigs. Particular examplesmay be directed to certain aspects and components of circumferentialmagnetizers for MFL pigs, including sensor heads, suspension systems forthe sensor heads, magnet bar wear pads, and the like. Additionalexamples may be directed to certain aspects and components of axialmagnetizers for MFL pigs, including sensor heads, suspension systems forthe sensor heads, magnet bar wear pads, and the like.

Circumferential Magnetizer Embodiment

With reference to FIG. 1, an exemplary embodiment of an MFL pigincluding circumferential magnetizers is shown. The MFL pig may includeseveral component bodies, including circumferential magnetizers 101,integrated electronic component body 102, and drive section componentbody 103. Each of circumferential magnetizers 101 may be offset from theother in order to ensure that the entire pipe surface to be inspected iscovered by the magnetic circuits and sensors. A geometry module 104 mayinclude mechanical arms for measuring deformations and the internaldiameter of the pipeline. An additional module 105 may include aninertial measurement unit for continuous mapping of the pipeline. One ormore battery modules 106 may be used to power all systems related to theinspection tool. A rear assembly module 107 may contain a transmitterand odometer. As will be appreciated by one of skill in the art, variousother sensors and electronic components may be included on an MFL pigdepending on the purpose of the pig and the intended measurements.

FIG. 2 presents a detailed view of the exemplary embodiment of the MFLpig shown in FIG. 1. The portion of the MFL pig shown in the embodimentof FIG. 2 includes three circumferential magnetizer modules 101. One ofskill in the art will appreciate that the component bodies shown neednot be in the particular order presented in the figure. The modularstructure of the component bodies may also enable easy repair of the pigby allowing a technician to swap out a component body in need of repair,thus allowing the pig to remain in service more continuously.

A circumferential magnetizer 101 in accordance with the presentdisclosure may include several components, including magnet systems,sensor systems, sensor suspension systems, magnet bar wear pads, andother related components. A circumferential magnetizer in accordancewith the present disclosure may include one or more magnets oriented andconfigured to induce a magnetic field transverse to the axis of thepipeline. In an embodiment, a magnetizer may include a plurality ofbanks of magnets disposed circumferentially around a central shaft of amagnetizer. In an embodiment, sensors may be disposed between the banksof magnets.

FIG. 3 presents a sectional schematic diagram of a circumferentialmagnetizer. Circumferential magnetizer 300 may include magnets 301,magnetic circuit poles 302, and sensors 304. Each magnet 301 andcorresponding magnetic circuit poles 302 may form a magnet bar. Theposition of the sensors 304 relative to the pipe wall and within themagnetic circuit can be seen. FIG. 3 illustrates the location 303 offlux leakage from the pipe wall and its relationship to the sensors.This diagram illustrates the general layout of components ofcircumferential 300 and is not necessarily drawn to scale. As will beappreciated by one of skill in the art, magnetic flux 303 will not bevisible, but its position is included for descriptive purposes. Magnets301 may be disposed at several locations in a circumferential directionabout circumferential magnetizer 300. Magnets 301 may include one ormore banks of magnets at each location. For example, FIG. 3 illustratesmagnets 301 at six circumferential locations; each location may includeone or more magnets 301 extending axially, which is not visible from thesectional schematic drawing. Magnetic circuit poles 302 may be providedto impart magnetic flux from magnets 301 to the interior of a pipe andthereby magnetize the pipe wall. Separate wear inserts may be coupled tomagnetic circuit poles 302 to extend the wear life of the mag bars.Sensors 304 may be positioned between magnetic circuit poles 302 tomonitor the magnetic flux through the pipe wall and detect magnetic fluxleakage.

As described above, a circumferential magnetizer may include a pluralityof magnets or a plurality of banks of magnets. The magnets, togetherwith the magnetic circuit poles, may form magnet bars. The magnet barsmay be spaced evenly apart from each other and may extend radiallyoutward from the central shaft, the central shaft being coaxial with thelength of the pipeline. For example, a circumferential magnetizer mayinclude two or more magnet bars, each magnet bar having a pair ofmagnetic circuit poles with the sensors disposed between the magneticcircuit poles. The sensor head may include a plurality of sensors. Themagnet bars may include a plurality of magnets, each magnet beingaligned in the same polarity. A magnetic circuit pole may contact onepole of a magnet and extend from the magnet radially outward toward apipe wall. Another magnetic circuit pole may contact the opposite poleof the magnet and extend from the magnet radially outward toward thepipe wall. A sensor head may be disposed between these magnetic circuitpoles. In this manner, a magnetic field may flow between the magneticcircuit poles and across the sensor head disposed between the magnetbars. When the magnetic circuit poles contact the pipe wall, a magneticcircuit may be created, and the sensors on the sensor head may monitorthe magnetic flux and detect any magnetic flux leakage from the pipewall.

In an embodiment, a circumferential magnetizer may include two or moremagnet bars, each including one or more magnets. In an embodiment, eachmagnet bar may include a plurality of magnets, each magnet having thesame orientation. Each magnet may include a first side having a firstpolarity and a second side having a polarity opposite to the firstpolarity. A first magnetic circuit pole may extend radially outward fromthe side of a magnet having a first polarity toward the pipe wall, and asecond magnetic circuit pole may extend radially outward from the sideof a magnet having the opposite polarity toward the pipe wall.Positioning magnets and magnetic circuit poles in this manner allows amagnetizer to impart a magnetic field circumferentially around theinterior of a pipeline in an orientation transverse to the axis of thepipeline. This orientation may allow for axially oriented defects, suchas a narrow axial metal loss or corrosion, loci of damage, some forms ofaxial cracking, or longitudinal seam weld defects extending axially downa portion of the pipeline to be detected.

The magnets in a circumferential magnetizer may be permanent magnets orelectromagnetic magnets. In an embodiment, the magnets may be rare-earthpermanent magnets. In an embodiment, the magnets may be neodymium-basedmagnets.

Each magnetic circuit pole may include one or more wear pads. A magneticcircuit pole wear pad may protect a magnetic circuit pole from theinterior surface of the pipeline or debris within the pipeline interior.This may extend the amount of usable time between repairs. In anembodiment, a magnetic circuit pole wear pad may comprise one or moreinserts. In a detailed embodiment, the magnetic circuit pole wear padmay comprise a plurality of carbide or ceramic inserts. In anembodiment, one or more magnetic circuit poles may include one or morecarbide or ceramic inserts disposed directly into the magnetic circuitpole(s). Carbide or ceramic inserts may provide beneficial reductions indrag force. Carbide or ceramic inserts may reduce drag force by as muchas 30% from conventional designs. Each magnetic circuit pole wear pad,if included, may be maintained at an angle with respect to the axis ofthe pipeline. A magnet bar wear pad, in an embodiment, may be arrangedand designed to facilitate slow counter-clockwise rotation of amagnetizer or pig. Alternatively or in addition, the carbide or ceramicinserts, if included, may be disposed in a pattern designed tofacilitate a slow rotation of the pig.

One or more sensor heads may be placed in each magnet bar. The one ormore sensor heads may be disposed between magnetic circuit poles and maytherefore be positioned to measure magnetic flux through a pipe wall.Each sensor head may include one or more sensors. The magnets maysaturate a portion of pipeline to be inspected with a circumferentialmagnetic field. The sensors may measure the magnetic field and, inparticular, may detect changes or aberrations in the magnetic field.Defects in the pipeline, including corroded areas, areas missing metal,geometric deformations, dents, buckles, wrinkles, cracks, and the likemay induce aberrations and changes into the magnetic field, or themagnetic field may leak at the particular location of a defect.

For example, FIG. 4 depicts a single magnet bar. Each magnet bar mayinclude magnets having a first (e.g., a south) polarity 401 and a second(e.g., a north polarity) 402 opposite to the first polarity 401. Notethat the nomenclature and particular polarity assigned for the purposesof the written description is largely arbitrary; for example, northcould be called positive, and south could be called negative. A southmagnetic circuit pole 401 may couple the south pole side of the magnetsto the pipe wall, and a north magnetic circuit pole 402 may couple thenorth pole side of the magnets to the pipe wall. Further, it isimportant that a sensor head be flanked on either side by magneticcircuit poles of opposing polarities to establish a magnetic fieldextending over and through the sensor head and sensors; this will beexplained in further detail later.

The circumferential magnetizers may travel through a pipe having aninternal diameter less than the nominal diameter of the magnetizer andmay be configured to closely articulate with the pipe wall. A pipe mayhave some structural aberration 404, such as a crack or crack-likeanomaly. The magnetic field from the magnets may be imparted to the pipewall by south magnetic circuit pole 401 and north magnetic circuit pole402. For visualization and descriptive purposes, magnetic flux lines 403are superimposed onto the diagram. Sensors may be placed between magnetsto be within the magnetic field. The magnetic field may be disruptedwhen the circumferential magnetizer passes over aberration 404, and thedisruption in the magnetic field may be detected by the sensors.

In an embodiment, a magnet bar may include a plurality of sensorsbetween each magnetic circuit pole to measure the magnetic flux impartedinto the pipe. FIG. 5 generally illustrates the placement of sensorsrelative to the magnets. FIG. 5 shows a circumferential magnetizerhaving magnets 501, magnetic circuit poles 502, and sensors 503. Sensors503 may be positioned between magnetic circuit poles 502. Magneticcircuit poles 502 may impart a magnetic flux into a pipe wall, and themagnetic flux may flow from one magnetic circuit pole to the other.Sensors 503 positioned within the magnetic field may take measurementsof the magnetic flux. In an embodiment, sensors 503 may takemeasurements of the magnetic flux as closely as every 0.039″ (1 mm) inthe axial direction of the pipe. In an embodiment, sensors 503 may takemeasurements of the magnetic flux as closely as every 0.050″ (1.25 mm)in the axial direction of the pipe. In an embodiment, sensors 503 maycomprise Hall-effect sensors. In an embodiment, a circumferentialmagnetizer may include six magnet bars and may have 72 Hall sensors perdiameter-inch. Aberrations in the pipe may cause distortions ordisruptions in the magnetic field, and the sensors may thus detect theirregularities in the magnetic field corresponding to the aberration inthe pipe. A magnetizer utilizing a circumferentially oriented magneticfield may be particularly adept at detecting axially oriented flaws andinspecting longitudinal welds of a pipeline. A magnetizer utilizing acircumferentially oriented magnetic field may be able to detect flaws of0.8 inches (20 mm) with an opening of 0.004″ (0.1 mm). A sensor head maybe able to survive forces of up to about 20 G, and sensors may be ableto withstand pressures of up to 2,000 psi (13.8 Mpa) and velocities ofup to 30 ft/s (9 m/s).

In an embodiment, each sensor head may include a plurality of sensors503. The plurality of sensors 503 may include Hall-effect sensors,eddy-current sensors, ultrasonic sensors (such as EMAT sensors), orcombinations thereof. The responses of each sensor may be combined andanalyzed to locate or define certain pipeline defects, as discussedabove. For example, a Hall-effect sensor may detect a response to amagnetic field leakage. The output of a Hall-effect sensor may varylinearly or nonlinearly with respect to changes in the magnetic field.These changes may reflect the presence of a flaw, defect, or anomaly.The output of a plurality of such sensors, in the aggregate, may allowfor an ultra-high resolution sampling in a given area of the internalpipe surface, thereby allowing defects to be accurately detected,characterized, analyzed, and quantified. In an embodiment, acircumferential magnetizer according to an aspect of the presentdisclosure may measure and store flux leakage values to a samplingdensity of up to 500 per square inch (80 square cm). In an embodiment, acircumferential magnetizer according to the present disclosure mayinclude several sensor heads, each sensor head having a plurality ofindividual sensors. In an embodiment, a pig may include threecircumferential magnetizer modules with six sensor heads per module and24 Hall-effect sensors per sensor head. This exemplary embodiment wouldyield a total of 432 Hall-effect sensors on the circumferentialmagnetizer. In an exemplary embodiment, a smart pig may have a diametergreater than six inches and contain three circumferential magnetizermodules, wherein each module includes six sensor heads and each sensorhead includes 24 Hall-effect sensors. Such a circumferential magnetizercould be said to have a sensor density of 72 sensors per diameter-inch.In an embodiment, a circumferential magnetizer may have a sensor densityof between about 60 to 100 sensors per diameter-inch.

A circumferential magnetizer may be sized to have a nominal diameterslightly larger than the diameter of a pipe. For example, acircumferential magnetizer slightly larger than six inches in diametermay be configured to travel through a six-inch pipe. One of skill in theart will recognize that a circumferential magnetizer according to thepresent disclosure may be sized to inspect pipes of alternate diameters.

FIG. 6 shows a top view of a magnet bar of a circumferential magnetizerin accordance with an embodiment of the present disclosure. In theembodiment shown in FIG. 6, a circumferential magnetizer may include anorth magnetic circuit pole 601 extending from a north-polarity side ofone or more magnets and a south magnetic circuit pole 602 extending froma south-polarity side of one or more magnets. When north magneticcircuit pole 601 and south magnetic circuit pole 602 contact a pipewall, a magnetic flux may extend between magnetic circuit poles 601,602. Sensor head 603 may be disposed between magnetic circuit poles 601,602. Sensor head 603 may include one or more sensors 604. In anembodiment, sensors 604 may be Hall-effect sensors. In an embodiment,there may be 24 sensors 604 disposed on sensor head 603. In anembodiment, the magnet bar of FIG. 6 may include one or more magnets. Inan embodiment, the magnet bar of FIG. 6 may include three magnets.

Magnetic circuit poles 601, 602 may contact the interior of thepipeline. In an embodiment, magnetic circuit poles 601, 602 may functionas a flux coupler to more efficiently saturate a pipe wall with amagnetic field. In a detailed embodiment, magnetic circuit poles 601,602 may include wear pads 605 on at least a portion of a surface thatcontacts the pipe wall. Wear pads 605 may comprise one or more ceramicor carbide inserts, as depicted in FIG. 6. Ceramic or carbide insertsmay protect the magnetic circuit poles from wear and may reduce dragforce. In an embodiment, ceramic or carbide inserts may reduce dragforce by about 30%.

FIG. 7 depicts a perspective view of a circumferential magnetizer inaccordance with an embodiment of the present disclosure. In theembodiment shown in FIG. 7, a circumferential magnetizer may includenorth magnetic circuit pole 701 extending from a north-polarity side ofone or more magnets, south magnetic circuit pole 702 extending from asouth-polarity side of one or more magnets, sensor head 703, and aplurality of sensors 704 disposed on sensor head 703. In an embodiment,sensors 704 may be Hall-effect sensors, and there may be 24 sensors 704disposed on sensor head 703. A sensor head wear pad 705 may be coupledto sensor head 703. Sensor head wear pad 705 may articulate with thepipe and may function to protect sensors 704.

Sensor head wear pad 705 may comprise a nickel-based alloy orsuperalloy. Magnetic circuit poles 701, 702 may include a ceramic insertor coating. In detailed embodiments, the ceramic may comprise siliconcarbide. In alternate detailed embodiments, the inserts may comprisetungsten carbide.

The circumferential magnetizer according to the embodiment depicted inFIG. 7 may include a means for collapsing 706 magnetic circuit poles701, 702. Means for collapsing 706 may comprise front links 707, upperlink 709, and torsion spring 708. Means for collapsing 706 may exert asufficient force, such as a spring force, to maintain the magneticcircuit poles 701, 702 in engagement with the pipe wall but maycollapse, entirely or partially, if the magnetic circuit poles 701, 702encounter an aberration in the pipe, such as an indentation, or if thepig including the circumferential magnetizer encounters a bend in thepipe. In an embodiment, sensor head 703 is also operatively coupled tothe means for collapsing 706. In an alternate embodiment, sensor head703 includes an independent sensor head suspension system. Sensor headsuspension system may include one or more conical springs coupling thebottom of the sensor head 703 to the central shaft. In an embodiment,sensor head suspension system comprises dual conical springs. Both meansfor collapsing 706 and sensor head suspension system may enablecomponents of the circumferential magnetizer to collapse up to 25% ofthe outside diameter of the pipe; that is, the diameter of at least partof the circumferential magnetizer may be reduced by up to 25% whenencountering an aberration in the pipe or when going around a bend inthe pipeline. These features may allow a pig to navigate pipeline bendsof greater than or equal to 1.5 D (where D is equal to the pipediameter). In an embodiment, these features may allow a pig to navigatepair of 1.5 D bends separated by a pipeline distance equal to 3D. Thecollapsibility features may reduce drag force on the circumferentialmagnetizer, which may help to prevent a pig from stalling whennavigating a relatively tight bend.

FIG. 8 shows a plurality of circumferential magnetizers according to anembodiment of the present disclosure operatively linked togethernavigating bends in a pipeline. A plurality of circumferentialmagnetizers 804 may be operatively linked together by linking means 805.Linking means 805 may be able to rotate about the center shaft and mayinclude features allowing for some transverse rotation about a boltincorporated in the linking means. These features of linking means 805can be seen with reference to FIG. 8. Each circumferential magnetizer804 may include a plurality of magnet bars 807. Each magnet bar 807 mayinclude magnetic circuit poles and one or more sensor head(s) 806including a plurality of sensors. A pig including circumferentialmagnetizers 804 may be capable of navigating complex bends in a pipeline801. For example, each bend 802, 803 may have a bend configuration ofgreater than or equal to about 1.5 D. In an embodiment, each bend 802,803 may have a bend configuration with a pair of 1.5 D bends separatedfrom each other by a pipeline distance equal to 3D. Circumferentialmagnetizers 804 may have a diameter of about six inches. If pipeline 801has a nominal diameter of six inches, there may be a distance of about18 inches between the bends 802, 803. Generally speaking,circumferential magnetizers 804 according to at least one embodiment ofthe present disclosure may be capable of navigating two bends 802, 803,where one magnetizer 804 simultaneously navigates each bend, if eachbend is separated by a distance of about three times the nominaldiameter of the pipe. A number of features may contribute to the abilityof a pig including three circumferential magnetizers to navigate suchcomplex bends without stalling, including but not limited to the meansfor collapsing the magnet bar, which provides the circumferentialmagnetizers with a collapsibility of about 25%; the length of the magnetbars and the center shaft; and the design of the universal joints, whichprovide connections among the various modules comprising the smart pig.These features may be seen with reference to FIG. 8.

A smart pig may be propelled through a pipe while product is movingthrough the pipe. The moving product may exert a pressure on an aft endof a smart pig, or on the aft end of one or more modules comprising asmart pig, which may propel the pig through the pipe. The speed at whicha pig and its constituent modules travels is accordingly a result of thedifferential pressure at an aft end of the pig compared to the forwardend of the pig. To take consistent measurements, it is desirable tomaintain the differential pressure as close to constant as possible tokeep the speed of the pig as close to constant as possible. Whenencountering a bend in a pipeline, conventional pigs tend to experienceincreased drag force that slows down and often stalls the pig in thepipeline. When a pig stalls, the differential pressure at the aft end ofthe pig builds until the pig is shot free. However, a pig that is shotin such a manner may be travelling too fast to take reliablemeasurements. This speed may also increase the risk of damage. The meansfor collapsing and the carbide wear inserts coupled to the magneticcircuit poles of circumferential magnetizer of the present disclosuremay help to reduce the drag force experienced in a bend, allowing thecircumferential magnetizer modules to maintain a constant speed througha bend, which may further enable more accurate measurements to be takenthroughout the pipeline, particularly in areas right after a bend. In anembodiment, a smart pig including three circumferential magnetizers maybe able to navigate a pair of 1.5 D bends separated from each other by apipeline distance equal to 3D.

FIG. 9 depicts the three circumferential magnetizers 901.Circumferential magnetizers 901 may be connected to each other withuniversal joints 903, which are connected to the central shaft bylinkage components 902. The universal joints may be angle controlled.The circumferential magnetizers 901 may be oriented relative to eachother to ensure complete, 360-degree coverage of the inside of a pipe.Universal joints 903 may maintain the orientations of thecircumferential magnetizers with respect to each other. The centralshaft, linkage components 902, and universal joints 903 may comprisetitanium to maintain strength, provide corrosion resistance, and reduceweight. In an embodiment, the central shaft, linkage components 902, anduniversal joints 903 may be comprised entirely of titanium.

FIG. 10 includes a front view 1001 and an isometric view 1002 of acircumferential magnetizer module according to an embodiment of thepresent disclosure. FIG. 10 shows that each module may have six magnetbars. Each magnet bar may provide approximately 120 degrees of pipe wallcoverage. Three modules may allow a pig to provide 360-degree coverage.Providing a smart pig with three modules may, for example, allowcomplete coverage in a six-inch pipe, but other tool diameters mayrequire a different number of bars or modules.

FIG. 11 provides a side view of a circumferential magnetizer moduleshowing just two bars and their respective means for collapsing. Meansfor collapsing includes upper and lower parallel links 1101, which jointhe magnet bars to the central shaft 1104. The parallel links ensurethat the magnet bars continually remain in good contact and parallel1102 to the pipe surface and central shaft 1104. The torsion springs1103 mounted on the upper link of each magnet bar keep the modulecentered and allow the magnet bars to collapse toward central shaft 1104when passing over obstacles or negotiating bends and other borerestrictions.

In an embodiment, each magnet bar may include rear links similar tolinks 1101 to join the rear end of each magnet bar to the central shaft1104, along with a torsion spring. Such an embodiment may maintain theentire magnet bar in contact with the pipe wall. Alternatively, as shownin FIG. 14, each magnet bar 1404 of a circumferential magnetizer mayinclude a front control link 1401 and a torsion spring 1402. Torsionspring 1402 may support the weight of each magnet bar and may help tosupport the weight of the central shaft. The rear portion of acircumferential magnetizer may include a polyurethane ring 1403.Polyurethane ring 1403 may help to maintain each magnet bar biasedagainst the pipe wall but may also help to balance forces, especiallywhen encountering aberrations in the pipeline or when navigating bends.Polyurethane ring 1403 may include bends 1404, which may allowpolyurethane ring 1403 to temporarily collapse and allow the magnetbar(s) to collapse toward the center shaft. Ring 1403 may be made frompolyurethane for durability and chemical resistance concerns; however,one of skill in the art may recognize alternative materials from whichring 1403 may be constructed, such as silicone or a durable,chemical-resistant thermoplastic.

FIG. 12 illustrates a side view of circumferential magnetizer module.The circumferential magnetizer according to the embodiment of FIG. 12includes magnetic circuit poles 1201. Magnetic circuit poles 1201 may becurved and thickened at their forward and aft ends. The curvature andend thickening, which is visible in FIG. 12, may help to concentrate themagnetic flux and create greater magnetic uniformity across sensor head1203. Sensor head 1203 may include a wear plate and may include a singleattachment point. The single attachment point may facilitate both radialmovement and internal surface curvature tracking.

FIG. 13 provides a sectional view of a circumferential magnetizer moduleaccording to an embodiment of the present disclosure. Thecircumferential magnetizer module may include a hollow central shaft1301, front universal joint 1302, rear universal joint 1303, magnets1304, magnet shields 1305, and upper and lower magnet bar to centershaft attachment links 1306, 1307. A circumferential magnetizer modulemay include a sensor head 1311, a plurality of sensors 1312 disposed onsensor head 1311, a wear pad 1313, and conical springs 1308 forsuspension of the sensor head 1311. FIG. 13 also illustrates thelocation of torsion spring 1310. Central shaft 1301 may extend touniversal joint limiter 1315, which limits the movement of the universaljoints 1303 and keeps the magnetizers in proper orientation with respectto one another to maintain 360-degree pipe wall coverage.

A sensor head 1311 may be in the shape of a sloping trapezoid. Theapproach angle of a sensor head according to such a design may minimizethe transmission of mechanical shocks and vibrations to the sensors andelectronics. Furthermore, such a sensor head design may provide a longerwear life, which may contribute to a longer inspection time of a smartpig between repairs. In an embodiment, one or more sensor heads 1311 mayextend radially outward and articulate with a surface of a pipeline totrack the pipeline surface. In an alternate embodiment, sensor head 1311may be shaped as a parallelogram or a rhomboid.

FIG. 15 presents a cross-sectional side view of an embodiment of acircumferential magnetizer including features already described herein.A plurality of magnet bars 1309 are attached to a central shaft 1502through a means for collapsing 706. The means for collapsing maycomprise a torsion spring 1310. Each magnet bar may include a sensorhead 1311, a plurality of sensors 1312 disposed on sensor head 1311, awear pad 1313, a sensor head base plate 1502, magnets 1304, magnetshields 1305, and conical springs 1308 for suspension of the sensor head1311.

Axial Magnetizer Embodiment

An MFL pig, in addition to or as an alternative to one or morecircumferential magnetizers, may include one or more axial magnetizers.An axial magnetizer in accordance with the present disclosure mayinclude several components, including magnet systems, sensor systems,sensor suspension systems, magnet bar wear pads, and other relatedcomponents. An axial magnetizer in accordance with the presentdisclosure may include one or more magnets oriented and configured toinduce a magnetic field coaxially with the axis of the pipeline. In anembodiment, an axial magnetizer may include a plurality of magnets of afirst polarity disposed circumferentially around a front end of acentral shaft as well as a plurality of magnets of the opposite polaritydisposed circumferentially around a rear end of the central shaft. In anembodiment, sensors may be disposed between the magnets having oppositepolarities.

With reference to FIG. 16, which shows two axial magnetizers 1601coupled together, an axial magnetizer may include a plurality of magnets1602, which may be coupled to the pipe wall with magnetic circuit poles1603, 1604. The magnets 1602, together with the magnetic circuit poles1603, 1604, may form magnet bars. The magnet bars may be spaced evenlyapart from each other and may extend radially outward from the centralshaft, the central shaft being coaxial with the length of the pipeline.For example, an axial magnetizer may include two or more magnet bars. Inan embodiment, an axial magnetizer may include six magnet bars. Eachmagnet bar may have a pair of magnetic circuit poles 1603, 1604 withsensors 1606 disposed between the magnetic circuit poles 1603, 1604. Asensor head 1605 may include a plurality of sensors 1606. Each magnetbar may include a magnet 1602A disposed toward the front end of themagnet bar having a first polarity and a magnet 1602B disposed towardthe rear end of the magnet bar having the opposite polarity. A frontmagnetic circuit pole 1603 may contact the first pole of the frontmagnet 1602A and extend from the magnet 1602A radially outward toward apipe wall. A rear magnetic circuit pole 1604 may contact the oppositepole (i.e., the opposite pole of the front magnet) of the rear magnet1602B and extend from the magnet 1602B radially outward toward the pipewall. A sensor head 1605 may be disposed between these magnetic circuitpoles. In this manner, a magnetic field may flow between the magneticcircuit poles and across the sensor head 1605 disposed between themagnet bars. When the magnetic circuit poles contact the pipe wall, amagnetic circuit may be created, and the sensors 1606 on the sensor head1605 may monitor the magnetic flux and detect any magnetic flux leakagefrom the pipe wall. Positioning magnets 1602 and magnetic circuit poles1603, 1604 in this manner allows a magnetizer to impart a magnetic fieldin an axial direction with respect to the axis of the pipeline. Thisorientation may allow for circumferentially oriented defects, such as ametal loss or corrosion at girth welds, loci of damage, some forms ofcircumferential cracking, or other defects extending circumferentiallyaround a portion of the pipeline to be detected.

The magnets 1602 in an axial magnetizer may be permanent magnets orelectromagnetic magnets. In an embodiment, the magnets may be rare-earthpermanent magnets. In an embodiment, the magnets may be neodymium-basedmagnets.

Axial magnetizers may be connected to each other with universal joints,which connected to the central shaft by linkage components 1607. Theuniversal joints 1608 may be angle controlled. The axial magnetizers maybe oriented relative to each other to ensure complete coverage of theinside of a pipe. Universal joints 1608 may maintain the orientations ofthe circumferential magnetizers with respect to each other. The centralshaft, linkage components 1607 and universal joints may comprisetitanium to maintain strength, provide corrosion resistance, and reduceweight. In an embodiment, the central shaft, linkage components 1607,and universal joints 1608 may be comprised entirely of titanium.

With reference to FIG. 17, each axial magnetizer may include six magnetbars 1701. Each magnet bar may be designed to cover about 30 degrees ofthe pipe circumference, such that when each axial magnetizer has sixmagnet bars, coupling two axial magnetizers to each other may coverabout 360 degrees of the pipe circumference. Each magnetic circuit polemay include one or more wear pads 1702. A magnetic circuit pole wear pad1702 may protect a magnetic circuit pole from the interior surface ofthe pipeline or debris within the pipeline interior. This may extend theamount of usable time between repairs. In an embodiment, a magneticcircuit pole wear pad 1702 may comprise one or more inserts 1703. In adetailed embodiment, the magnetic circuit pole wear pad 1702 maycomprise a plurality of carbide or ceramic inserts 1703. In anembodiment, one or more magnetic circuit poles may include one or morecarbide or ceramic inserts 1703 disposed directly into the magneticcircuit pole(s). Carbide or ceramic inserts 1703 may provide beneficialreductions in drag force. Carbide or ceramic inserts 1703 may reducedrag force by as much as 30% from conventional designs. Each magneticcircuit pole wear pad 1702, if included, may be maintained at an anglewith respect to the axis of the pipeline. A magnet bar wear pad, in anembodiment, may be arranged and designed to facilitate slowcounter-clockwise rotation of a magnetizer or pig. Alternatively or inaddition, the carbide or ceramic inserts 1703, if included, may bedisposed in a pattern designed to facilitate a slow rotation of the pig.

One or more sensor heads may be placed in each magnet bar. The one ormore sensor heads may be disposed between magnetic circuit poles and maytherefore be positioned to measure magnetic flux through a pipe wall.Each sensor head may include one or more sensors. The magnets maysaturate a portion of pipeline to be inspected with an axial magneticflux. The sensors may measure the magnetic flux and, in particular, maydetect changes or aberrations in the magnetic flux. Defects in thepipeline, including corroded areas, areas missing metal, geometricdeformations, dents, buckles, wrinkles, cracks, and the like may induceaberrations and changes into the magnetic flux, or the magnetic flux mayleak at the particular location of a defect.

The axial magnetizers may travel through a pipe having an internaldiameter less than the nominal diameter of the magnetizer and may beconfigured to closely articulate with the pipe wall. A pipe may havesome structural aberration, such as a crack or crack-like anomaly. Anaxial magnetizer may be particularly adept at detectingcircumferentially oriented aberrations or defects. The magnetic fieldfrom the magnets may be imparted to the pipe wall by front magneticcircuit pole and rear magnetic circuit pole (each having oppositepolarities) to saturate the pipe wall with magnetic flux. Sensors may beplaced between magnets to be within the magnetic field. The magneticfield may be disrupted when the axial magnetizers pass over aberrationsor flaws, and the disruption in the magnetic flux may be detected by thesensors.

In an embodiment, a magnet bar may include a plurality of sensorsbetween each magnetic circuit pole to measure the magnetic flux impartedinto the pipe. The magnetic circuit poles may impart a magnetic fluxinto a pipe wall, and the magnetic flux may flow from one magneticcircuit pole to the other. Sensors positioned within the magnetic fieldmay measure the magnetic flux. In an embodiment, sensors may be spacedat approximately 0.080 inches (2.0 mm). In an embodiment, sensors maycomprise Hall-effect sensors. In an embodiment, an axial magnetizer mayinclude six magnet bars and may have 40 Hall sensors per diameter-inch.Aberrations in the pipe may cause distortions or disruptions in themagnetic field, and the sensors may thus detect the irregularities inthe magnetic field corresponding to the aberration in the pipe. Amagnetizer utilizing an axially oriented magnetic field may be able todetect circumferential flaws of 0.8 inches (20 mm) with an opening of0.004″ (0.1 mm). A sensor head may be able to survive forces of up toabout 20 G, and sensors may be able to withstand pressures of up to2,000 psi (13.8 Mpa) and velocities of up to 30 ft/s (9 m/s).

In an embodiment, each sensor head may include a plurality of sensors.The plurality of sensors may include Hall-effect sensors, eddy-currentsensors, ultrasonic sensors (such as EMAT sensors), or combinationsthereof. The responses of each sensor may be combined and analyzed tolocate or define certain pipeline defects, as discussed above. Forexample, a Hall-effect sensor may detect a response to a magnetic fieldleakage. The output of a Hall-effect sensor may vary linearly ornonlinearly with respect to changes in the magnetic field. These changesmay reflect the presence of a flaw, defect, or anomaly. The output of aplurality of such sensors, in the aggregate, may allow for an ultra-highresolution sampling in a given area of the internal pipe surface,thereby allowing defects to be accurately detected, characterized,analyzed, and quantified. In an embodiment, an axial magnetizeraccording to an aspect of the present disclosure may measure and storeflux leakage values to a sampling density of up to 320 per square inch(50 square cm). In an embodiment, an axial magnetizer according to thepresent disclosure may include several sensor heads, each sensor headhaving a plurality of individual sensors. In an embodiment, a pig mayinclude two axial magnetizer modules with six sensor heads per moduleand 24 Hall-effect sensors per sensor head. In an exemplary embodiment,a smart pig may have a diameter greater than six inches and contain twoaxial magnetizer modules, wherein each module includes six sensor heads.In an embodiment, an axial magnetizer may have a sensor density ofbetween about 30 to 100 sensors per diameter-inch.

An axial magnetizer may be sized to have a nominal diameter slightlylarger than the diameter of a pipe. For example, an axial magnetizerslightly larger than six inches in diameter may be configured to travelthrough a six-inch pipe. One of skill in the art will recognize that anaxial magnetizer according to the present disclosure may be sized toinspect pipes of alternate diameters. An axial magnetizer may includecompression features allowing the magnetizer to fit inside and travelwithin the pipe.

With reference back to FIG. 16, magnetic circuit poles 1603, 1604 maycontact the interior of the pipeline. In an embodiment, magnetic circuitpoles 1603, 1604 may function as a flux coupler to more efficientlysaturate a pipe wall with a magnetic field. In a detailed embodiment,magnetic circuit poles 1603, 1604 may include wear pads 1702 on at leasta portion of a surface that contacts the pipe wall. Wear pads 1702 maycomprise one or more ceramic or carbide inserts 1703, as depicted inFIG. 17. Ceramic or carbide inserts 1703 may protect the magneticcircuit poles 1603, 1604 from wear and may reduce drag force. In anembodiment, ceramic or carbide inserts 1703 may reduce drag force byabout 30%.

Sensor head wear pad 1702 may comprise a nickel-based alloy orsuperalloy. Magnetic circuit poles 1603, 1604 may include a ceramicinsert 1703 or coating. In detailed embodiments, the ceramic maycomprise silicon carbide. In alternate detailed embodiments, the insertsmay comprise tungsten carbide. Other varieties will be apparent to thoseskilled in the art.

The axial magnetizer according to the embodiment depicted in FIG. 18 mayinclude a means for collapsing the magnet bars. Means for collapsing maycomprise front links 1801 and torsion spring 1802. Torsion spring 1802may exert a sufficient force, such as a spring force, to maintain themagnetic circuit poles 1603, 1604 in engagement with the pipe wall butmay collapse, entirely or partially, if the magnetic circuit poles 1603,1604 encounter an aberration in the pipe, such as an indentation, or ifthe pig including the axial magnetizer encounters a bend in the pipe. Inan embodiment, sensor head 1605 is also operatively coupled to the meansfor collapsing by virtue of it being part of the magnet bar. In analternate embodiment, sensor head 1605 includes an independent sensorhead suspension system. Sensor head suspension system may include one ormore conical springs 1805 coupling the bottom of the sensor head 1605 tothe magnet bar. In an embodiment, sensor head suspension systemcomprises dual conical springs 1805. Both means for collapsing andsensor head suspension system may enable components of the axialmagnetizer to collapse up to 25% of the outside diameter of the pipe;that is, the diameter of at least part of the axial magnetizer may bereduced by up to 25% when encountering an aberration in the pipe or whengoing around a bend in the pipeline. These features may allow a pig tonavigate pipeline bends of greater than or equal to 1.5 D (where D isequal to the pipe diameter). In an embodiment, these features may allowa pig to navigate pipeline bends with a minimum separation of 2D (i.e.,two pipe diameters separation). In another embodiment, the features mayallow a pig to navigate a pair of 1.5 D bends separated from each otherby a pipeline distance equal to 3D. The collapsibility features mayreduce drag force on the axial magnetizer, which may help to prevent apig from stalling when navigating a relatively tight bend.

In an embodiment, each magnet bar may include rear links similar tolinks 1801 to join the rear end of each magnet bar to the central shaft,along with a torsion spring. Such an embodiment may maintain the entiremagnet bar in contact with the pipe wall. Alternatively, each magnet barof an axial magnetizer may include a front control link 1801 and atorsion spring 1802. Torsion spring 1802 may support the weight of eachmagnet bar and may help to support the weight of the central shaft. Therear portion of the axial magnetizer may include a polyurethane ring1808. Polyurethane ring 1808 may help to maintain each magnet bar biasedagainst the pipe wall but may also help to balance forces, especiallywhen encountering aberrations in the pipeline or when navigating bends.Polyurethane ring 1808 may include bends 1809, which may allowpolyurethane ring 1808 to temporarily collapse and allow the magnetbar(s) to collapse toward the center shaft. Ring 1808 may be made frompolyurethane for durability and chemical resistance concerns; however,one of skill in the art may recognize alternative materials from whichring 1808 may be constructed, such as silicone or a durable,chemical-resistant thermoplastic.

A sensor head may be in the shape of a sloping trapezoid. The approachangle of a sensor head according to such a design may minimize thetransmission of mechanical shocks and vibrations to the sensors andelectronics. Furthermore, such a sensor head design may provide a longerwear life, which may contribute to a longer inspection time of a smartpig between repairs. In an embodiment, one or more sensor heads mayextend radially outward and articulate with a surface of a pipeline totrack the pipeline surface. In an alternate embodiment, sensor head maybe shaped as a parallelogram or a rhomboid.

FIG. 19 presents a cross-sectional side view of an embodiment of anaxial magnetizer. The embodiment of FIG. 19 may include a central shaft1901 running approximately through the axial magnetizer's central axisand providing a central support for other elements. A front universaljoint 1902 and a rear universal joint 1903 may be coupled to respectiveends of the central shaft 1901. Front universal joint 1902 and rearuniversal joint 1903 may couple the axial magnetizer to one or moreother modules of a pig, such as another axial magnetizer, an electronicsmodule, a mapping module, a circumferential magnetizer, or the like. Inan embodiment, front universal joint 1902 and rear universal joint 1903may be able to rotate about central shaft 1901. In an embodiment,central shaft 1901 may extend to universal joint limiter 1907, which maylimit the movement of the universal joints 1902, 1903. For example, iftwo axial magnetizers connected by universal joints have a limitedrotational movement, the magnetizers may maintain a consistentorientation with respect to each other to maintain 360-degree pipe wallcoverage. Front universal joint 1902 and rear universal joint 1903 maybe coupled to central shaft 1901 by a bolt or similar couplingmechanism, about which the universal joints 1902, 1903 may pivot. Theability of universal joints 1902, 1903 to pivot may allow the pig,including the axial magnetizer, to better navigate sharper bends in thepipeline. For example, a pig including an axial magnetizer according tothe embodiment described in FIG. 19 may be capable of negotiating a 3D(where D is equal to the nominal pipe diameter) pipe bend radius. Inanother example, the pig may be able to navigate a pair of 1.5 D bendsseparated from each other by a pipeline distance equal to 3D.

An axial magnetizer according to an embodiment such as that illustratedin FIG. 19 may include one or more magnet bars. In an embodiment, anaxial magnetizer may include six magnet bars, each providingapproximately 30 degrees of pipe wall coverage. Each magnet bar may becoupled to the center shaft 1901 at the front end with a magnet bar link1905 at magnet-bar-to-center-shaft connection 1904. Connection 1904 mayinclude a bolt (or other similar coupling mechanism) about which magnetbar link 1905 may rotate or pivot. The ability of the magnet bar torotate or pivot about connection 1904 may allow the magnet bar tocollapse toward the center shaft 1901. In an embodiment, thecollapsibility of each magnet bar may allow an axial magnetizer toreduce its cross-sectional diameter by about 25%. This may allow themagnetizer to navigate tighter turns than would otherwise be possiblewithout becoming stuck or stalled. Without becoming stalled around abend, a pig with an axial magnetizer according to the present disclosuremay be able to maintain more consistent speed—even around tightbends—and thus may maintain more a more complete measurement of thepipeline. In contrast, if a pig stalls around a bend, pressure may buildup behind the pig, eventually shooting the pig forward through the bendat a velocity that is too high to take measurements of the pipeline,thus reducing the quality of the inspection. A torsion spring 1906 maybe included at the connection between the magnet bar and the magnet barlink 1905 to support the weight of the magnet bar and to maintain themagnet bar in a biased position against the pipe wall, while stillallowing for collapsibility when necessary. In an embodiment, apolyurethane ring 1908 may couple the rear end of the magnet bar to thecenter shaft 1901. Polyurethane ring 1908 may include an outward bend(e.g., a rearward-facing bend), which may allow the magnet bar tocollapse toward the center shaft when encountering a sufficient force(e.g., a pipe aberration or bend). Polyurethane ring 1908 may alsoabsorb shock.

Each magnet bar may include front magnet(s) 1910A. Front magnet(s) 1910Amay have a first polarity. Each front magnet 1910A has the same polarityas the other front magnets, such as front magnet(s) 1910C. Rearmagnet(s) 1910B may have the opposite polarity as front magnet 1910A.Each rear magnet 1910B had the same polarity as the other rear magnets,such as rear magnet(s) 1910D. Each magnet bar may include one or moremagnet shields 1911. Magnet shields 1911 may help to focus the magneticfield from the magnets to allow more efficient transfer of magnetic fluxthrough the pipe wall and, accordingly, more consistent, accurate, andefficient measurements to be taken. Each magnet bar may include a sensorhead 1920, which may include a wear pad, upon which Hall effect sensors1921 may be disposed. Sensor head may further include a sensor board1923 and a sensor head base plate 1924. For example, sensor board 1923may be a printed circuit board providing support and electricalconnectivity to Hall effect sensors 1921. Each sensor head 1920 mayinclude one or more conical springs 1922 coupling the sensor head 1920to the magnet bar. In an embodiment, each sensor head 1920 is coupled toits respective magnet bar by dual conical springs 1922. Conical springs1922 may support the sensor head 1920, may keep the sensor headpositioned against a pipe wall, and may allow for collapsibility whenencountering an aberration or bend in the pipeline.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting.

1.-10. (canceled)
 11. An axial magnetizer module for a smart pig,comprising: a central shaft; and at least one magnet bar, coupled to thecentral shaft by a means for collapsing, and inducing a magnetic fieldcoaxially to a longitudinal axis of the central shaft, the at least onemagnet bar comprising: a first magnet of a first polaritycircumferentially disposed around a front end of the central shaft; asecond magnet of a second polarity circumferentially disposed around arear end of the central shaft; a front magnetic circuit pole coupled tothe first magnet and extending radially outward from the central shaft;and a rear magnetic circuit pole coupled to the second magnet andextending radially outward from the central shaft; a sensor head tomonitor magnetic flux comprising at least one sensor disposed betweenthe front magnetic circuit pole and rear magnetic circuit pole.
 12. Theaxial magnetizer module of claim 11, wherein the means for collapsingcomprises a torsion spring to allow the magnet bar to move radiallyinward toward the central shaft.
 13. The axial magnetizer module ofclaim 11, wherein the first magnet and second magnet are rare-earthpermanent magnets, electromagnets, or neodymium-based magnets.
 14. Theaxial magnetizer module of claim 11, wherein the at least one sensorincludes one or more of: a Hall-effect sensor and an ultrasonic sensor.15. The axial magnetizer module of claim 14, comprising six magnet barsand forty Hall-effect sensors.
 16. The axial magnetizer module of claim11, wherein the front magnetic circuit pole and the rear magneticcircuit pole include a plurality of wear pads.
 17. The axial magnetizermodule of claim 11, wherein the sensor head has a sloping trapezoid,rhomboid, rectangle, or parallelogram shape.
 18. The axial magnetizermodule of claim 11, wherein the sensor head further comprises asuspension system comprising at least one conical spring to position thesensor head during operation.
 19. The axial magnetizer module of claim11, further comprising a magnet shield to focus the induced magneticfield.
 20. The axial magnetizer module of claim 11, further comprising ajoint extending axially from the central shaft to link an additionalmodule of the smart pig.